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Subject: Re: [hwloc-devel] hwloc support added in Grid Engine / Grid Scheduler
From: Jeff Squyres (jsquyres_at_[hidden])
Date: 2011-04-13 16:47:45

On Apr 13, 2011, at 1:32 PM, Brice Goglin wrote:

> Don't worry about the depth. Even if you have less levels of caches in
> some parts of the machine, or no hyperthreading or whatever different,
> we still build levels of identical objects. So you still get a
> consistent depth for all cores, threads, sockets, and different levels
> of caches. But obviously, you will see less objects when iterating
> through levels within the "smaller" part of the machine.

This would be good to add to the documentation; I've been doing manual traversals of hwloc trees just to future-proof/heterogeneous-proof my code (because I didn't know that the depth would always be the same for a given object type even if some branches don't have all object types).

So let's say I have a (fictitious) machine with one socket with an L1 and L2 cache for its cores, and another socket that only has an L1 cache for its cores:

                / \
      socket 0 socket 1
        L2 L1
        L1 core

If I traverse down through children in the tree, are you saying that there will be some kind of fake/empty object in the right sub tree corresponding to where the L2 is in the left sub tree?

Jeff Squyres
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